We wish to use synchrotron radiation techniques to determine the 3D structure of the A1 domain of human von Willebrand factor (vWF). The information gained from this project will help clarify the mechanisms and regulation of a key event essential for normal hemostasis and also involved in pathological thrombosis. Crystallization of native vWF is considered impossible with currently available techniques due to the large size and heterogeneous nature of the molecule; thus the only approach to gain information on the 3D structure of vWF is to focus on isolated domains. The results expected from our studies will help in defining the vWF-GP Ib contact sites and will assist in searching for specific inhibitors of vWF binding to GP Ib, an important target for anti-thrombotic intervention.